As compared with glass, a transparent resin material has various advantages in that it is excellent in lightweightness, impact resistance and shapability and is economical; and recently, resin is being much used for optical glass in the art of optical components such as lenses and others.
One typical transparent thermoplastic resin material is a polycarbonate resin. In particular, a polycarbonate resin produced by the use of 2,2-bis(4-hydroxyphenyl)propane (generally called bisphenol A) as a starting material has many advantages in that it is excellent in transparency, more lightweight than glass and excellent in impact resistance and that it is applicable to industrial-scale mass-production of shaped articles as being able to be shaped in melt; and therefore the resin of the type is being much used as optical components in various fields. The resin has a relatively high refractive index of 1.58 or so, but its Abbe's number indicating the degree of refractivity dispersiveness is around 30 and is low, or that is, the resin is poor in the balance between the refractivity and the dispersiveness characteristic thereof. At present, therefore, the resin is limited in point of the range of its applications to optical components. For example, regarding lenses for spectacles that are one typical example of optical components, it is known that the materials for those lenses preferably have an Abbe's number of at least 40 when the visibility function thereof is taken into consideration (Quarterly Journal of Chemical Review, No. 39, Refractivity Control of Transparent Polymer, edited by the Chemical Society of Japan); and in case where a polycarbonate resin produced by the use of bisphenol A as a starting material is directly used for those lenses as it is, the lenses formed of the resin could hardly have the desired characteristics.
JP-A 2003-73564 reports a technique of dispersing inorganic fine particles having a high refractive index in a resin matrix having an alicyclic structure and having a high Abbe's number, thereby realizing an organic-inorganic hybrid material having an increased refractive index. In this, however, the transparency and the strength of the resin may be lowered, and the material produced therein could not be said to be always sufficient in practical use.
JP-A 2007-238929 describes an organic-inorganic hybrid material comprising inorganic fine particles and a thermoplastic resin having a functional group capable of forming a chemical bond with inorganic fine particles, and the material satisfies both high refractivity and good transparency. However, the technique is not always sufficient in practical use in that the organic-inorganic hybrid material produced could not satisfy both good heat resistance and a high Abbe's number.
Recently, the releasability from mold in molding an organic-inorganic hybrid material therein has brought about a new problem in the art. In an organic-inorganic hybrid material, the organic material has a functional group so as to promote the adsorbability thereof to the inorganic material and the dispersibility thereof in the formed material. Accordingly, the functional group in the organic material often closely adheres to the mold where the hybrid material is molded, therefore bringing about a problem in that the molded article may be scratched when it is released from the mold. From this viewpoint, the mold releasability of the hybrid material is a serious point. At present, however, no one has succeeded in developing an organic-inorganic hybrid material capable of completely solving the problem of mold releasability thereof on a practical level.
Accordingly, no one knows a thermoplastic material which satisfies all the requirements of high refractivity, low dispersiveness (high Abbe's number), heat resistance, transparency and lightweightness, of which the refractive index can be controlled in any desired manner, and which is excellent in the releasability from mold, and optical components comprising the material; and it is earnestly desired to develop them.